The present disclosure pertains to lubricating greases that are useful and effective in underwater applications, that are resistant to water wash-out, and that do not off-gas toxic volatile compounds.
Specialized underwater structures, such as submarine hangar areas, have actuated parts, such as dry dock shelter operating hatches and other hatches and doors, that must be adequately lubricated to ensure long service-life. There is an ongoing need to develop a new lubricating grease resistant to seawater washout and free from harmful gases that can leach out into the breathable airspace. Greases that are resistant to water washout are usually petroleum byproduct based and off-gas high levels of substances that are deemed harmful. Many fluorocarbon based greases that do not leach out any dangerous gases do not stick to the steel submarine hatches, and wash away when flushed with seawater. Previous and current commercial, government, and military applications have used certain hydrocarbon-based greases (including Termalene®, Bel-Ray Company, Inc., Farmingdale, N.J.). However, these greases have been found to off-gas toxic compounds such as isopropanol and low molecular weight hydrocarbons in pressurized environments, making them unacceptable for use in the high pressure environments (up to six atm) and enclosed areas encountered in diving operations. To ensure diver safety in these operations, fluorocarbon-based greases (including DuPont Krytox® 240AC, DuPont Fluoroproducts, Wilmington, Del. and Halocarbon 25-5S, Halocarbon Products Corp., River Edge, N.J.), which do not off-gas toxic compounds are utilized. While the lubrication performance of these materials is exceptional, the resistance to seawater washout is very low, necessitating constant and costly reapplication of the lubricant.
The performance of fluorocarbon-based lubricants comes at a premium price, which can be $100/oz or higher, depending on the material. Coupled with the high rate of seawater washout, the continued use of these products is a significant cost in terms of money spent on maintenance. In addition to the high material cost, specialized underwater structures such as submarines must also spend more time in maintenance while the grease is constantly reapplied. The resultant costs in terms of both time and money while these structures are out of service must be mitigated. To rectify this situation, a grease formulation that is safe for underwater operations such as diving (does not off-gas toxic compounds), delivers high lubrication performance (at least equal to that of the currently used fluorocarbon-based greases), and is resistant to seawater washout is actively being sought.